We will continue to evaluate the role of steroid profile and thyroid hormone profile monitoring in optimizing both diagnosis and treatment of different endocrine diseases. We developed a state of the art micro assay for 11 steroids by LCMSMS. This assay has been used to optimize the treatment of patients with CAH (Dr Merke, collaborator)and adrenal diseases(Dr Stratakis, and Dr Niemen). We have also shown that there is a statistically significant diurnal fluctuation in steroid concentrations for all steroids tested except progesterone. The extent of this diurnal variation is so large that it clearly necessitates development of new time dependent reference intervals. Manuscript published in Clinical Chemistry , J Steroid Biochem Mol Biol., and Endocrine Connections. We will assess the role of NPY IN PREECLAMPSIA and ENDOMETRIOSIS. We will also examine the role of our new free steroid profile and free 25 OH Vitamin D3 assays in health and disease. The work described above has been published in numerous papers, a few of which are listed below. 1. Welsh KJ, Soldin SJ.,DIAGNOSIS OF ENDOCRINE DISEASE: How reliable are free thyroid and total T3 hormone assays? Eur J Endocrinol. 2016 Dec;175(6):R255-R263. Review. 2. Nella AA, Mallappa A, Perritt AF, Gounden V, Kumar P, Sinaii N, Daley LA, Ling A, Liu CY, Soldin SJ, Merke DP. A phase 2 study of continuous subcutaneous hydrocortisone infusion in adults with congenital adrenal hyperplasia. J Clin Endocrinol Metab 2016 Dec;101(12):4690-4698. 3. Welsh KJ, Stolze BR, Yu X, Podsiadlo TR, Kim LS, Soldin SJ Assessment of thyroid function in intensive care unit patients by liquid chromatography tandem mass spectrometry methods.Clin Biochem. 2017:50;318-22. 4. Wei SM, Baller EB, Kohn PD, Kippenhan JS, Kolachana B, Soldin SJ, Rubinow DR, Schmidt PJ, Berman KF.Mol Psychiatry. 2017 Apr 18. doi: 10.1038/mp.2017.72. Epub ahead of print Brain-derived neurotrophic factor Val66Met genotype and ovarian steroids interactively modulate working memory-related hippocampal function in women: a multimodal neuroimaging study. 5. Nilubol N, Soldin SJ, Patel D, Rwenji M, Gu J, Masika LS, Chang R, Stratakis CA, Kebebew E.11-Deoxycortisol may be superior to cortisol in confirming a successful adrenal vein catheterization without cosyntropin: a pilot study Int J Endocr Oncol. 2017 May;4(2):75-83. 6. Hannah-Shmouni F, Soldin SJ. Thyroid Hormone Therapy for Older Adults with Subclinical Hypothyroidism.N Engl J Med. 2017 Oct 5;377(14):e20. doi: 10.1056/NEJMc1709989. PMID:29019377 7. Parikh TP1, Stolze BR2, Ozarda Ilcol Y3, Jonklaas J4, Welsh K5, Masika LS6, Hill MJ7, DeCherney AH8, Soldin SJ9 Diurnal variation of steroid hormones and reference intervals using mass spectrometric analysis. Endocr Connect. 7, 13541361. 8 Ling C, Sun Q, Khang J, Felipa Lastarria M, Strong J, Stolze B, Yu X, Parikh TP, Waldman MA, Welsh K, Jonklaas J, Masika L, Soldin SJ. . Does TSH Reliably Detect Hypothyroid Patients? Ann Thyroid Res. 2018;4(1):122-125. 9. Sheikh SI et al TSH should not be used as a single marker of thyroid function. Annals Thyroid Research 2018;4:0151-4. 11. Mallappa A, Nella AA, Sinaii N, Rao H, Gounden V, Perritt AF, Kumar P, Ling A, Liu CY, Soldin SJ, Merke DP. Long-term Use of Continuous Subcutaneous Hydrocortisone Infusion Therapy in Patients with Congenital Adrenal Hyperplasia.Clin Endocrinol (Oxf). 2018 Jul 13. doi: 10.1111/cen.13813 12. Sun Q, Gu J, Stolze BR, Soldin SJ.Atmospheric Pressure Chemical Ionization is a Suboptimal Ionization Source for Steroids.Clin Chem. 2018 64(6):974-976 13.Carla Frare1,2, Mackenzie E. Jenkins1, Steven J. Soldin3,4 and Kelly L. Drew1,2* The Raphe Pallidus and the Hypothalamic-Pituitary-Thyroid Axis Gate Seaso nal Changes in Thermoregulation in the Hibernating Arctic Ground Squirrel (Urocitellus parryii) Frontiers in Physiology 2018 Volume 9 Article 1747